On mobile, the website list at /sites does not have any X padding. The
elements touch the screen left and right. This corrects it by wrapping
the list in a div with "px-4" on it.
This could also be achieved by setting "px-4" and "md:px-0" on every
element but it is unecessarily complex and if some more elements
appeared on this screen, it would be easy to forget this. A container
should be in charge of this, which is what is proposed here.
